1. Field of the Invention
The present invention relates to a pivot arm, one end of which is to be mounted on a stationary support or other such carrier, or is to be attached to an apparatus, specifically a medical apparatus, that can be moved up and down and pivoted in a plane; having two mounting bolts or supports that are always parallel and are connected with each other by at least one cross-member that is hinged to both bolts or supports by parallel pivot axles; having a spring housing in which a helical compression spring that is supported indirectly on the spring housing and a connecting rod that holds a spring support stationary relative to the bar are arranged, and which spring housing is hinged to at least one of the two mounting bolts or supports by means of at least one coupling.
2. Description of the Prior Art
In a known pivot or shear arm of this type, two constantly parallel cross-members are provided to form a variable parallelogram with the two mounting supports. The separate spring housing is arranged on one of the two constantly parallel cross-members between the two such cross-members, whereby a single coupling provides the articulated connection to the mounting support to mount one end of the pivot arm on a stationary support. The two cross-members can laterally overlap one another, at least when arranged horizontally; but this does not assure that dust, lubricant or particles produced by wear that are present in the cross-members or the spring housing cannot pass through the hinge points of the cross-members and the coupling and, for example, endanger a medical operation being performed by means of an apparatus arranged on the coupling-remote mounting support of the pivot arm for this apparatus.